Teensy audio - Mic IN interférence

[Viking]

I am working on an Audio project with a teensy 4.0 and an audio shield rev D.

I have no problem with the code, everything works perfectly.

I use the jack input to broadcast the sound via a Breakout card.

And for the microphone, I did 79 tests, and whatever the microphone, the amplifier card with microphone...

I have a problem with digital noise that is recorded on the audio track.

if I replace the microphone with a resistor, I only have the recording of this digital noise.

I checked the soldering, I have the impression that they are good.

I tried with shielded cable, it did not change anything.

I even did tests with RC filter for the microphone, always the same problem.

I managed to extract it via AI.

In the photo the upper oscillation is the clear and limpid voice, and the lower one this constant and persistent noise.

Have you already had this problem and how to solve it please?

Thank you all.


Ps : the audio problem here : https://drive.google.com/file/d/13kRxXXGdNEfsTrPtCG6nNchfR9wf_RHS/view?usp=sharing


Pss :
I tested on the computer's USB, on a suitable charger and on a powerboost 1000c with a 3.7v 4400mah battery.

it's the same noise every time.

 

[TomChiron]

You could try this: disconnect any USB and other connection to a computer. Use a powerbank to power the teensy. Connect headphones to the headphone output of the audioshield. Change your sketch that the microphone input is routed to the headphone output.
This way you can check if the problem is coming from any noise introduced from the PC USB (which I would assume) or if there is something with your Teensy/audioshield.

 

[Viking]

You could try this: disconnect any USB and other connection to a computer. Use a powerbank to power the teensy. Connect headphones to the headphone output of the audioshield. Change your sketch that the microphone input is routed to the headphone output.
This way you can check if the problem is coming from any noise introduced from the PC USB (which I would assume) or if there is something with your Teensy/audioshield.

I tested on the computer's USB, on a suitable charger and on a powerboost 1000c with a 3.7v 4400mah battery.

it's the same noise every time.

 

[Pio]

I use the jack input to broadcast the sound via a Breakout card.

If this means that you are connecting the jack on the AudioAdaptorBoard to an external device, like an amplifier or an audio interface, then it might be the problem. This Jack is a headphone output, referenced to a virtual ground (which is not the same as normal signal GND). This output should be used with headphones only.
From the SGTL5000 datasheet:

HP_VGND Note: Do not connect HP_VGND to system
ground, even when unused. This is a virtual ground (DC
voltage) that should never connect to an actual “0 Volt
ground”. Use the widest, shortest trace possible for the
HP_VGND.

Try using a Line Output available on the IDC10 connector.

 

[Viking]

If this means that you are connecting the jack on the AudioAdaptorBoard to an external device, like an amplifier or an audio interface, then it might be the problem. This Jack is a headphone output, referenced to a virtual ground (which is not the same as normal signal GND). This output should be used with headphones only.
From the SGTL5000 datasheet:

Try using a Line Output available on the IDC10 connector.

Yes the Jack is connected to the jack of my sparkfun trrs breakout card,

And the card with 2 cable to my HP.

This one


I Will try with a headphone directly

 

[MarkT]

Use the line outputs if connecting to anything other than headphones/earbuds.
BTW I have measured some artifacts on the SGTL5000 microphone inputs, IIRC something like a low level tone around 13kHz or some such - plotting the spectrum is a good way to see what's in there.

 

[Viking]

From this video :

And i've check on this 20 pages off similar project (here : https://forum.pjrc.com/index.php?threads/teensy-4-0-based-audio-guestbook.70553/)


I tried without the breakout, but it doesn't change anything, in itself it is not powered, it converts the 2 wires of the speaker into a Jack.
But even with headphones the problem is still present.

apparently it would correspond to writing on the SD card because some have managed to remove the noise by switching to a teensy 4.1 and recording on the 4.1 card and no longer on the audioshield card.

But I know that some manage to make the teensy 4.0 and audioshield work clearly.

does anyone have a lead to explore please?